Hydraulic transmission



Jan. 12, 1937. E. SEIBOLD 2,067,209

HYDRAULIC TRANSMISSION Original Filed Oct. '7, 1933 Sheets-Sheet l\NVENTOR msT BHBOLD iz aYQ Q M'TORNEY Jan. 12, 1937. E. SEIBOLD2,067,209

HYDRAULIC TRANSMISSION Original Filed Oct. 7, 1933 2 Sheets-Sheet 2 24 I25 \NVENTOR ERNSTSQBOLD %v Q) Patented Jan. 12, 1937 UNITED STATESPATENT OFFICE HYDRAULIC TRANSMISSION Voith Original application October7, 1933, Serial No. 692,664. Divided and this application June 19, 1934,Serial No. 731,247. In Germany October Claims.

This invention relates to hydraulic transmissions and methods foroperating the same, and more particularly to improvements in suchtransmissions as are generally known as the Foettinger 5 type. Theinvention finds application to power transmission devices, such ashydraulic slip couplings, hydraulic torque changers, and as well tohydraulic variable speed transmissions, and the like.

This application is a divisional of my copending application Serial No.692,664, filed in the United States Patent Oflice on October '7, 1933.

As is known in the art, each one of the beforementioned transmissiondevices consists gener- 5 ally of these parts,-a primary and a secondaryshaft, one or more primary and secondary wheels, whereby in the case ofthe hydraulic variable speed transmission, an hydraulic slip couplingmay be combined to form one unit with a torque changer. The operationfor these units is made possible through the medium of a working fluid.This working fluid is supplied from a reservoir by a pump to thetransmission.

One object of the invention is to arrange the g5 reservoir which holdsthe supply of working fluid, in a position close to the pump whichserves to supply the transmission. with working fluid,

and with the reservoir placed below the transmission to have the pumpbelow the reservoir or be- 30 low the liquid level of the reservoir. Bythis arrangement, the supply and return of oil can be effected in a veryeflicient manner.

A further object of this invention consists in providing means to makepossible the equaliza- 35 tion of .pressure between the air spacesof thetransmission and the reservoir, and preferably to so place the air ventas to avoid the loss of liquid. In the operation of devices of thiskind, it has been shown that the liquid which passes 40 to the reservoiralways absorbs or entrains air.

By this intermingling with air, a strong transposition of air from thetransmission to the reservoir may take place, whereby an iniuriousunderpressure in the transmission and 2. correspond-- 45 ingover-pressure in the reservoir may result.

These conditions are undesirable for many reasons, and are unavoidable,for instance, in such transmissions in which connecting conduits betweenthe reservoir and the different parts of 60 the transmission exist,particularly in such cases where the conduits, for certain reasons,terminate below the liquid level in the reservoir.

If then there is a lower pressure in the transmission and a higherpressure in the reservoir, 55 by these pressures liquid is forced backinto such produced an unexpected decrease in the loss inherent in theapparatus. Also, liquid losses from the reservoir are avoided due to thefact that pressure increase in the reservoir is avoided. Tests whichhave been made have demonstrated surprisingly favorable results fromthis improvement.

Preferably, the embodiment provides forthe arrangement of the airconnection at so high a position that liquid losses are avoided.Finally, when changing over from one part of the transmission to anotherpart, it has been found that the discharge of air from the part to befllled 'with liquid and the inflow of air into the part to be emptied ofthe liquid, take place much more rapidly and more eficiently. To assistthis operation, special air openings are provided for each part of thetransmission, whereby an exceedingly rapid exchange of air between thetransmission, the housing, and the casing, takes place.

These and further features of the invention will be hereinafterdescribed, with the aid of the accompanying drawings; and the inventionwill be finally pointed out in the appended claims.

In the accompanying drawings:-

Figure 1 shows a side elevation of an hydraulic transmission in whichthe pump is at the lowest point of the liquid reservoir;

Figure 2 shows a side elevation partly in section, of another embodimentof my invention in which all of the essential operative parts arebrought within a unitary container;

Figure 3 shows a side elevation partly in section in which the apparatusshown is provided with an air vent.

Figure 4 is a section of a torque changer; Figure 5 is a section of aslip coupling; and Figure 6 is a section of an hydraulic variable speedtransmission composed of a torque changer, a slip coupling, and areservoir for the working fluid.

Similar characters of reference indicate cor'- responding partsthroughout the various views.

' for several seconds.

Referring now'to Figure 1. the hydraulic transmission is connected withthe discharge conduit II which in turn is connected with the reservoir|2, the latter being provided with an overflow edge l3, and such edge I3is lower than the lowest point of the operating parts of thetransmission 25. At the lowest point of this reservoir l2, a supply pumpI4 is provided, and this pump is connected with the hydraulictransmission 25 by means of the conduit l5. For a very eflicient workingof the parts described, an air-equalizing pipe 33 brings aboutcommunication of air between the transmission 25 and reservoir l2.

This arrangement is especially advantageous when operated in such amanner that during the starting period of the transmission the supplypump is driven with a higher number of revolutions than that necessaryto keep the transmission filled when in normal operation. One obtains bythis a short starting period. The necessary larger starting power of thesupply pump is of no importance asv it is required only In ordinarynormal operation, the supply pump is required to run only with so smalla number of revolutions as is necessary to maintain the transmissionfilled, and the power requirement in such a. case is small. To obtainthe above higher number of revolutions, in the simplest manner, thesupply pump is driven by an electric motor l6 capable of running with atleast two different speeds, and the switch I! for this motor iscorrespondingly provided with at least two operating positions. Thesepositions are so arranged that from the zero position In the positionofhigh-speed revolution llb must first be passed through, and

only by further movement of the switch to position H0, is the lowermotor speed provided for normal operation obtained. The electric circuitis completed by conductors l8 and |8a and electrical source of supplyHi. This electrical connection is described as a preferred form but isnot essential to the invention herein claimed.

Particularly import-ant are the advantages of this arrangement inhydraulic transmissions in which during the operation, the liquid isallowed to dissipate from one part of the transmission, whereby the sameisemptied, and is supplied to another part of the transmission for thepurpose of filling it. In such a case, one uses, on the pressure side ofthe supply pump, a multiple way valve, indicated by 32 in Fig. 3 and. by23 in Fig. 6, which connects piping either with the slip coupling or thetorque changer parts of the transmission.

In the embodiment shown in Fig. 2, the transmission, the control valveand the supply pump are all assembled in the form of one unitaryselfcontained unit wherein the reservoir for the liquid is made of avery simple and inexpensive vessel and is fastened to the transmissionin such a way that the pump, the control valve and all connections areenclosed by the reservoir container. In this embodiment shown in Fig. 2,the conducting parts 20, 2| and 22, the control valve 23, and the pump24, are brought together in. a unitary manner within the reservoir 26.The pump 24 is actuated by shaft 21 of the transmission by means of theworm 28 and the worm gear 29. Thus by the operation of shaft 21,

and the'rotation of the worm gear 29, the Worm 28 and the shaft 30 aredriven, whereby the pump 24 is operated, and the liquid forced throughthe conduits 20, 2| and 22 suitably controlled by the valve 23. Theworking fluid after having been pumped into the transmission throughpipe 22, discharges at 20. It will be noted that all of these operatingparts are within the reservoir 26 and that the parts are of the simplestconstruction. It will also be noted that the connection of the variousconduits 20, 2| and 22 are within the liquid of the reservoir 26 so thatno harm results from any leakage. To bring about a very eiiicientoperation of the parts described, an air-equalizing pipe 33 connects thetransmission and the reservoir, whereby the air pressure therein isequalized.

In the embodiment of Figure 3, a conduit 3| conducts operating liquidfrom the control valve 32 to the transmission 25. The air spaces of thetransmission 25 and of the reservoir 26 are interconnected by an airpipe 33, which through a branch pipe 34 communicates with the atmosphereat its upper end 35, this end 35 being relatively high in respect to theother parts of the apparatus in order to avoid liquid losses. The liquidis returned from the transmission to the reservoir by pipe 36. Thesupply pump 31 is operated by the motor 38. In case the extension 34 beomitted the pipe 33 can be arranged as shown in Figs. 1 and 2.

The transmission shown in Figs. 1 to 3 may have either of the forms"shown in Figs. 4 to 6. In Figure 4 is shown a section of a torquechanger having a casing 56 in which a primary shaft 4| and secondaryshaft 46 rotate, primary shaft 4| being rotated by the prime mover 51.On the primary shaft 4| is an impeller 42 fixed thereto. On thesecondary shaft in fixed connection with same is a turbine runner havingtwo stages 43 and 45. Between the two stages 43 and 45 is a fixed guidewheel 44, fixed to the housing 56. Working fiuid is admitted to thetorque changer through the opening 58 and the working fluid isdischarged at 59 and 60.

In Figure 5 is shown a slip coupling in which the primary shaft 4| issecured to the impeller 41 and the secondary shaft 46 is secured to theturbine wheel 48. Inlet of the working fluid is shown at 6| and outletfor the same at 62.

In Fig. 6 is shown a combined torque changer and slip coupling. Thetorque changer as well as the slip coupling consists of substantiallythe same parts as the parts described in connection with Figs. 4 and 5.Below the structure shown in Fig. 6 is shown a reservoir 26 and pump 24.A control valve 23, has a handle 52, which may be turned in eitherdirection as shown by the arrow 63, and the working fluid directedeither in the direction 55 to the slip coupling or in the direction 54to the torque changer. While Fig. 6 shows a reservoir, it is of courseclear that a reservoir is used in Figs. 1 and 2, in which case adistributing valve is not necessary.

I have described several embodiments of my invention, but changes may bemade therein without departing from the spirit or scope of the inventionas defined in the appended claims.

I claim:-

1. In an hydraulic transmission which, by means of filling with oremptying of a working fluid, can be put into operation or put out ofoperation, respectively; a housing for the transmission, a pump for theworking fluid, a motor for the pump, a reservoir for the working fluidthe highest level of which is below the lowest point of the workingfluid in the transmission, said reservoir being separate from andindependent of said transmission housing the pump being at a the airspace in contact with the working fluid,

in the reservoir for equalizing the pressure between said air spaces,said stationary pipe providing air communication continuously betweenthe uppermost part of the transmission and the reservoir. 1

2. In an hydraulic transmission which, by

means of filling with or emptying of a working fluid, can be put intooperation or put out of operation, respectively; a housing for thetransmission, a pump for the working fluid, a motor for the pump, areservoir for the working fluid the highest level of which is below thelowest point of the working fluid in the transmission, said reservoirbeing separate from and independent of said transmission housing, thepump being at a lower elevation than the level of the working fluid inthe reservoir, said pump being within the reservoir, supply and returnpipes to and from the transmission and the reservoir, and a stationarypipe connecting the air space in the uppermost part of the transmissionhousing with the air space in contact with the working fluid, in thereservoir for equalizing the pressure between said air spaces, saidstationary pipe providing air communication continuously between theuppermost part of the transmission and the reservoir.

3. In an hydraulic transmission which, by means of filling with oremptying of a working fluid, can be put into or put out of operation,respectively; a housing for the transmission, a pump for the workingfluid, a motor for the pump, a reservoir for the working fluid thehighest level of which is below the lowest point of the working fluid inthe transmission, the pump being at a lower elevation than the level ofthe working fluid in the reservoir, supply and return pipes to and fromthe transmission and the reservoir, a stationary pipe connecting the airspace in the uppermost part of the transmission housing with the airspace in the reservoir for equalizing the pressure between said airspaces, said stationary pipe providing air communication continuouslybetween the uppermost part of the transmission and the reservoir, andmeans in said last-named pipe having an opening in communication withthe outside atmosphere at a plane which does not permit any liquid lossthrough said opening.

4. In an hydraulic transmission which, by means of filling with oremptying of a working fluid, can be put into operation or put out 01'operation, respectively; a housing for the transmission, a pump for theworking fluid, a motor for the pump, a reservoir for the working fluidthe highest level of which is below the lowestpoint of the working fluidin the transmission, said reservoir being separate from and independentof said transmission housing, the pump being at a lower elevation thanthe level of the working fluid in the reservoir, supply and return pipesto and from the transmission and the reservoir, the transmission andreservoir being built as a unit and said reservoir enclosing said pumpand pipes, a primary shaft, a driving mechanism between the primaryshaft and the supply pump for effecting the operation of the supply pumpupon the actuation of the primary shaft, and a stationary pipeconnecting the air space in the uppermost part of the transmissionhousing with the air space in contact with the working fluid, in thereservoir for equalizing the pressure between said air spaces, saidstationary pipe providing unrestricted air communication continuouslybetween the uppermost part of the transmission and the reservoir.

5. In an hydraulic transmission which, by means ,of filling with oremptying of a working fluid, can be put into operation or put out ofoperation, respectively; a housing for the transmission, a pump for theworking fluid a motor for the pump, a reservoir for the working fluid,said reservoir being separate from the transmission housing, supply andreturn pipes to and from the transmission and reservoir, and astationary pipe connecting the air space in the uppermost part of thetransmission housing with the air space in contact with the workingfluid in the reservoir for equalizing the pressure between said airspaces, said stationary pipe providing unrestricted air communicationcontinuously between the uppermost part the transmission and thereservoir;

ERNST SEIBOLD.

